This is a five year application for participation in the NIMH Cooperative Agreement to establish Diagnostic Centers for Psychiatric Linkage Studies in Bipolar Illness. During the first year of the Project a standardized Assessment Battery of acceptable reliability will be developed. All adult admissions to inpatient services at Washington University Department of Psychiatry will be screened resulting in approximately 360 Bipolar patients per year. Based on pilot data, this will provide approximately 27 multiplex families per year. These families will include at least two siblings with Bipolar or Schizoaffective Bipolar Disorder (DSM-III-R Criteria) who are willing to cooperate in the linkage study. During years two to four of the award, we will ascertain and study 66 multiplex nuclear families which will be extended to second and third degree relatives to increase the number of secondary cases. Approximately 535 relatives will be included in the study and it is anticipated that the database will include several large extended pedigrees. Psychiatric assessments and blood samples for lymphoblastoid cell lines will be obtained from each subject. This application has several special strengths. Firstly, it would be complemented by an NIMH Clinical Research Center in Psychiatric genetics a', Washington University. Secondly, the principal investigators have extensive experience in studying the genetics of Bipolar Affective Disorder including the design and execution of psychiatric linkage studies. Thirdly, the department has much experience in developing, standardizing and implementing psychiatric assessments. The expertise of the investigators in psychiatric genetics in general and the affective disorders in particular would be useful to the proposed cooperative agreement between NIMH and three extramural sites.